Sir Keir Starmer was on Tuesday night branded China's 'useful idiot' as he prepared to approve its plan for a mega–embassy in London despite a growing backlash from his MPs.

The Prime Minister was accused of planning a 'craven kowtow' to the Chinese in return for new trade and investment deals to boost Britain's flagging economy when he makes his first trip to Beijing later this month.

He also faced allegations that he is ignoring the threat to national security posed by the plan for Europe's biggest diplomatic mission, after blueprints showed it will feature a hidden chamber just a metre away from sensitive cables that transmit financial data to the City of London.

Not one MP defended the Government's expected planning approval in the Commons today, while seven Labour backbenchers spoke up against it, highlighting human rights abuses in China as well as intimidation of Hongkongers in the UK.

Nine Labour MPs also wrote to Communities Secretary Steve Reed, who must make the final decision on the application before Tuesday, urging him to reject it. 

Local residents are already gearing up to bring a legal challenge if he does give it the green light.

And on Tuesday it was reported that the White House remains 'deeply concerned' about the plans, and that the UK has had to reassure its allies – including the US – that no sensitive data is transferred through the cables next to the embassy.

In the Commons, the Government was even rebuked by Speaker Sir Lindsay Hoyle for sending a housing minister instead of someone from the Home Office to answer MPs' concerns about repression and espionage conducted from the alleged spy hub.

It can also be revealed that the Metropolitan Police has apologised for failing to investigate Chinese officials who were accused of carrying out surveillance on protesters at the embassy site opposite the Tower of London. 

Shadow Home Secretary Chris Philp said: 'It is shameful that our Prime Minister is planning a craven kowtow to the Chinese... to persuade them to bail him out of the economic mess he and Rachel Reeves have created. 

'He is putting our national security at risk by acting as Peking's poodle. By dancing to [Chinese president] Xi Jinping's tune, Keir Starmer is acting as the ultimate useful idiot.'

Luke de Pulford, of the Inter–Parliamentary Alliance on China, said: 'The embassy issue goes far beyond party politics, touching on key matters of national security. 

'Not a single MP spoke in favour of the plans, reflecting public opinion which is firmly against having a monstrous spy base in the heart of London.

'It takes a lot of guts to stand up when your own party is backed into a corner. 

'The PM should listen to these courageous Labour MPs, or he will certainly regret it as and when the decision is challenged in the courts.'

In the Commons, Shadow Home Office minister Alicia Kearns said the plans revealed that the Chinese Communist Party wants to build '208 secret rooms and a hidden chamber' alongside the crucial fibre optic cables, adding: 'We now know it plans to demolish the wall between the cables and the embassy cables on which our economy is dependent.' 

She added: 'Labour promised a new relationship with China, yet UK goods exports are down 23 per cent. Surrendering our security for trade was always a bad policy, but surrendering our security while exports plummet is, frankly, insanity.'

Leading opposition from Labour MPs, Commons international development committee chairman Sarah Champion said: 'Government agencies and departments have raised concerns. 

'Our international partners have raised concerns. I want my Government to stand up to bullies, not to reward them.'

A Whitehall source said: 'The embassy will be approved. It is just a matter of timing. There is a benefit in consolidating the sites China uses into one location.'